In a semiconductor device for use in a computer, miniaturization of the wiring width referred to as a design rule has advanced year after year in order to realize a higher integration and an increase in speed. Therefore, a case where substrate surface defects of nanometer scale, which have not been treated as problems heretofore, adversely affect on the performance of the semiconductor device has increased. Therefore, the importance of overcoming the substrate surface defects with nanometer scale has increased.
Among semiconductor substrates, a polishing composition containing silica particles and a water-soluble polymer is preferably used for silicon wafer polishing. When a silicon wafer is polished with a polishing composition disclosed in Patent Document 1, a protective film derived from a water-soluble polymer is formed on the silicon wafer surface after polishing. Since the protective film imparts hydrophilicity to the substrate surface after polishing, it is becoming easy to handle the substrate after polishing. However, the water-soluble polymer for use in the polishing composition has hundreds of thousands or more of molecular weights, and therefore may form an aggregate with the silica particles. The aggregate containing the silica particles and the water-soluble polymer may cause a substrate surface defect referred to as a Light Point Defect (LPD).
In order to reduce the LPD resulting from the aggregate containing the silica particles and the water-soluble polymer, it is important to eliminate the aggregate from the polishing composition. Then, Patent Document 2 has proposed adding a surfactant and the like to a polishing composition to increase the dispersibility of abrasives. Patent Document 3 has proposed compounding an aggregation inhibitor in a polishing composition to thereby provide a polishing composition having high dispersibility of abrasives while imparting high hydrophilicity to the substrate surface after polishing.
Moreover, in final polishing of a silicon wafer, it is important to prevent not only the LPD resulting from an aggregate but contamination with metals and metallic compounds, particularly nickel (Ni) and copper (Cu).